JP4865845B2 - Alkaline battery and method for producing the same - Google Patents

Description

  The present invention relates to an alkaline dry battery that is a primary battery, and more particularly, to an improvement in a negative electrode current collector of an alkaline dry battery.

Conventionally, alkaline batteries have been widely used as power sources for electronic devices such as portable devices.
The alkaline dry battery comprises a hollow cylindrical positive electrode mixture containing a positive electrode active material, a gelled negative electrode containing a negative electrode active material filled in a hollow portion of the positive electrode mixture, the positive electrode mixture and the gel negative electrode. A separator disposed therebetween, a negative electrode current collector inserted into the gelled negative electrode, and a negative electrode terminal plate electrically connected to the negative electrode current collector. For the negative electrode current collector, brass mainly composed of copper is used.

When an alkaline battery is overdischarged, hydrogen gas is generated and electrolyte leakage (hereinafter referred to as leakage) may occur. It is considered that the leakage mechanism is related to the elution of the constituent elements of the negative electrode current collector into the electrolyte. Therefore, various studies have been conducted on the negative electrode current collector of alkaline dry batteries.
For example, Patent Document 1 proposes that the surface of brass be plated with at least one metal selected from the group consisting of zinc, tin, and lead in order to suppress generation of hydrogen gas from the negative electrode current collector. Has been. Thereby, generation of hydrogen gas from the negative electrode current collector is suppressed.

  Patent Document 2 proposes that a tin plating layer is formed on the surface of brass and the thickness thereof is 0.05 to 0.5 μm. Thereby, the liquid leakage at the time of overdischarge can be suppressed.

Japanese Patent Laid-Open No. 5-13085 JP 2006-172908 A

  It is known that when an assembled battery in which a plurality of alkaline dry batteries are connected in series is in an overdischarged state, at least one of the batteries constituting the assembled battery inevitably reverses its polarity. For example, a battery having a small electric capacity may be reversed. Even when the electric capacity of the batteries is the same, due to the difference in internal resistance and the surface area of the active material, the same discharge history is not passed, and the battery with a low discharge voltage is reversed. In the reversed battery, copper and zinc are eluted from the brass constituting the current collector. As a result, the hydrogen generation overvoltage of zinc decreases, the amount of hydrogen gas generation increases, and the reversed battery leaks. Such battery leakage is particularly likely to occur when the discharge circuit of the assembled battery including the reversed battery is released. The proposals in Patent Documents 1 and 2 are insufficient to prevent such leakage.

  Accordingly, an object of the present invention is to provide a highly reliable alkaline dry battery in which gas generation during overdischarge is suppressed and a method for manufacturing the same in order to solve the above-described conventional problems.

One aspect of the alkaline dry battery of the present invention is a hollow cylindrical positive electrode mixture containing a positive electrode active material, a gelled negative electrode containing a negative electrode active material filled in a hollow portion of the positive electrode mixture, and the positive electrode mixture A separator disposed between the gelled negative electrode, a negative electrode current collector inserted into the gelled negative electrode, a negative electrode terminal plate electrically connected to the negative electrode current collector, and an electrolyte solution. An alkaline battery comprising:
The negative electrode current collector is made of brass having an average crystal particle diameter of 0.015 mm or more, and the brass contains 30 to 40% by weight of zinc .

The average crystal particle diameter of the brass is preferably 0.030 mm to 0.1 mm, and more preferably 0.045 mm to 0.1 mm.
The negative electrode current collector has a nail shape, and has a round bar-shaped body portion inserted into the gelled negative electrode, and a top portion provided at one end of the body portion, and the top portion includes the negative electrode terminal plate. It is preferable that the diameter of the trunk is 0.95 to 1.35 mm.
The brass, zinc 3 0-40 wt% of at least one 0.05-3 wt% is selected from tin, the group consisting of phosphorus and aluminum as an optional component, and the balance consisting of copper and unavoidable impurities Is preferred.

The positive electrode active material preferably contains at least one of manganese dioxide and nickel oxyhydroxide.
The negative electrode active material preferably contains zinc or a zinc alloy.
The zinc alloy preferably contains 150 to 500 ppm of Al.
The ratio of the capacity Cn of the gelled negative electrode to the capacity Cp of the positive electrode mixture: Cn / Cp is preferably 0.95 to 1.10.

It is one aspect of a method for producing an alkaline dry battery of the present invention,
(1) obtaining a nail-shaped product made of brass containing zinc 30 to 40% by weight,
(2) heating the molded body to 300 ° C. or higher;
(3) After the step (2), the molded body is cooled at a rate of 10 ° C./second or less to obtain a negative electrode current collector having an average crystal particle diameter of the brass of 0.015 mm or more;
including.

  According to the present invention, it is possible to obtain a highly reliable alkaline dry battery in which gas generation during overdischarge is suppressed. In an assembled battery in which multiple alkaline batteries with different capacity between batteries are connected in series, even if a battery with a small capacity is reversed, gas generation of the reversed battery is suppressed and the leakage resistance of the battery is improved. To do.

It is a front view which makes a part of AA alkaline dry battery concerning one embodiment of the present invention a section.

Hereinafter, the mechanism of gas generation accompanying the elution of brass during conventional overdischarge will be described.
At the start of discharge of the alkaline battery, the reactions of the following formulas (1) and (2) proceed. At the positive electrode, the reduction reaction of manganese dioxide proceeds. In the negative electrode, zinc is dissolved, and the generated zinc oxide is deposited on the surface of zinc.
Positive electrode: MnO ₂ + H ⁺ + e ⁻ → MnOOH (1)
Negative electrode: Zn + 4OH ⁻ → Zn (OH) ₄ ²⁻ + 2e ⁻ (2)
Zn (OH) ₄ ^2- → ZnO + H ₂ O + 2OH ⁻

At the end of discharge of the alkaline battery, the moisture in the negative electrode decreases, so that supply of OH ⁻ to zinc cannot catch up, and the OH ⁻ concentration near the zinc surface decreases. The vicinity of the zinc surface becomes locally acidic, and the zinc becomes passivated. For this reason, the negative electrode potential increases rapidly, and the battery voltage decreases rapidly. When the load is constant, the current value also decreases rapidly.

Hereinafter, an example of discharging an assembled battery in which a plurality of alkaline dry batteries are connected in series will be described.
When a resistor is connected to an assembled battery in which two batteries A and B are connected in series and the circuit is closed, the assembled battery is discharged. When the capacity of the battery A is smaller than that of the battery B, in the battery A, the zinc becomes non-conductive before the battery B, the battery voltage rapidly decreases, and the battery is in the final discharge state. When the discharge of the assembled battery further proceeds, in the battery A, the battery voltage shows a negative value (becomes a value of 0 V or less), and inversion occurs.
In the reversed battery A, it is necessary to take out electrons from the negative electrode side even though zinc is inactivated. In order to supply these electrons, the metal elutes from the negative electrode current collector as ions. For example, when the negative electrode current collector is made of brass and has tin plating, a metal such as zinc deposited on the negative electrode current collector surface (metal eluted from the active material), tin, zinc in brass, copper in brass Elute in order. Most of the metal eluted from the negative electrode current collector is copper or zinc constituting brass.

When the discharge circuit including the reversed battery A is opened, the passivation of zinc is eliminated, the negative electrode potential is lowered, and the zinc original potential is approached. At this time, the negative electrode potential is lower than the hydrogen gas generation potential, and hydrogen gas is easily generated.
Metals, such as copper, eluted during the reversal of the poles reduce the hydrogen generation overvoltage of zinc. For this reason, the hydrogen gas generation rate increases, the amount of hydrogen gas generation increases, and the battery internal pressure increases. When the battery internal pressure exceeds a predetermined value, the predetermined safety valve breaks and leaks.

An embodiment of the alkaline dry battery of the present invention will be described with reference to FIG. FIG. 1 is a front view of a cross section of a part of an AA alkaline battery (LR6). An arrow X in FIG. 1 indicates the axial direction of the battery (positive electrode mixture).
A hollow cylindrical positive electrode mixture 2 is accommodated in a bottomed cylindrical battery case 1. The positive electrode mixture 2 is in close contact with the inner surface of the battery case 1 and is in electrical contact with the battery case that also serves as the positive electrode current collector. A graphite coating layer is formed on the inner surface of the battery case 1 in order to reduce contact resistance with the positive electrode mixture. A convex positive electrode terminal 1 a is provided at the bottom of the battery case 1. The battery case 1 is obtained, for example, by press-molding a nickel-plated steel sheet into a predetermined size and shape.

  A gelled negative electrode 3 is filled in the hollow portion of the positive electrode mixture 2 via a bottomed cylindrical separator 4. For the separator 4, for example, a nonwoven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber is used.

The opening of the battery case 1 is sealed by a sealing unit 9. The sealing unit 9 includes a nail-type negative electrode current collector 6, a resin gasket 5 having a safety valve, and a negative electrode terminal plate 7 in electrical contact with the negative electrode current collector 6.
The negative electrode terminal plate 7 has a central flat portion and a flange portion provided on a peripheral portion of the flat portion. The negative electrode terminal plate 7 has a hole 7a for releasing the gas in the battery to the outside at the boundary between the flange portion and the flat portion. The negative electrode terminal plate 7 is obtained, for example, by press-molding a nickel-plated steel plate or a tin-plated steel plate into a predetermined size and shape.

The negative electrode current collector 6 has a substantially cylindrical body portion 6a and a top portion 6b provided at one end of the body portion 6a. The top portion 6 b of the negative electrode current collector is welded to the flat portion of the negative electrode terminal plate 7.
The trunk portion 6a of the negative electrode current collector 6 is inserted into the central portion of the gelled negative electrode 3 by a predetermined length so that its axial direction is substantially parallel to the X direction. A cross section perpendicular to the X direction of the body portion 6a is substantially circular.

The negative electrode current collector 6 is made of brass having an average crystal particle diameter of 0.015 mm or more. By increasing the average crystal particle diameter of brass to 0.015 mm or more, the area of grain boundaries, that is, the reaction area of brass (the area where metal elution occurs) decreases. Therefore, elution of brass into the electrolyte during overdischarge is suppressed. Thereby, the fall of the hydrogen generation | occurrence | production overvoltage of zinc by the elution of brass is suppressed, and the leakage resistance of a battery improves.
In order to effectively suppress the elution of brass, it is preferable that the average crystal particle diameter is 0.015 mm or more at least in a region having a depth of 0.2 mm from the surface of the body of the negative electrode current collector. .

Moreover, since the average crystal particle diameter of brass is as large as 0.015 mm or more, the flexibility of the negative electrode current collector is improved. For this reason, even when the negative electrode current collector is slightly bent when the negative electrode current collector is press-fitted into the through hole of the gasket at the time of producing the sealing unit, it is corrected. Therefore, productivity is improved.
From the viewpoint of improving leakage resistance during battery overdischarge and improving productivity, the average crystal particle diameter of brass is preferably 0.030 mm or more, and more preferably 0.045 mm or more. The average crystal particle diameter of brass is about 0.1 mm at the maximum.

The average crystal particle diameter of brass is obtained, for example, by the following method.
A cross-sectional image perpendicular to the axial direction X of the body 6a is obtained with a polarizing microscope or the like. An area from the surface to a predetermined depth (for example, 0.03-0.2 mm from the surface) is set, and a line segment having a predetermined length P (for example, 50 to 100 μm) is placed at an arbitrary position within the area. Draw. The number Q of crystal grains completely divided by this line segment is obtained. And the crystal particle diameter R is calculated | required from a following formula.
Crystal particle diameter R = length of line segment P / number of crystal particles Q
This operation is repeated a plurality of times (for example, 5 to 10 times), and the crystal particle diameter R is obtained. The average value is defined as the average crystal particle size.

Brass is an alloy containing copper and zinc. However, brass can further include at least one selected from the group consisting of tin, phosphorus, and aluminum. The content of elements other than copper and zinc in brass is preferably 0.05 to 3% by weight.
From the viewpoint of current collection and strength, the brass preferably contains 30 to 40% by weight of zinc. If the zinc content of the brass is less than 30% by weight, the mechanical strength of the brass is lowered, the negative electrode current collector is easily bent, and the productivity is lowered. In addition, the cost increases. If the zinc content of the brass exceeds 40% by weight, the brass becomes brittle and the workability decreases.

From the viewpoint of current collection and strength, the diameter of the body portion 6a is preferably 0.95 to 1.35 mm. When the diameter of the body portion 6a is 1.35 mm or less, the contact area between the negative electrode current collector and the gelled negative electrode (electrolytic solution) is reduced, and gas generation from the negative electrode current collector is significantly suppressed. When the diameter of the body portion 6a is less than 0.95 mm, the mechanical strength is lowered, the negative electrode current collector is easily bent, and the productivity is lowered.
The length of the portion inserted into the gelled negative electrode of the body portion 6a / (the total length of the body portion 6a) is preferably 0.72 to 0.86. The length of the portion inserted into the gelled negative electrode of the body 6a / (filling height of the gelled negative electrode) is preferably 0.72 to 0.86. Thereby, in the part inserted in the gel-like negative electrode 3 of the negative electrode collector 6, the gel-like negative electrode 3 and the negative electrode collector 6 fully contact, and a favorable current collection effect is acquired.

In the alkaline dry battery of the present invention, the negative electrode current collector can be produced by the following method. That is, the method for producing the alkaline dry battery of the present invention comprises:
(1) obtaining a nail-shaped product made of brass,
(2) heating the molded body to 300 ° C. or higher;
(3) After the step (2), the molded body is cooled at a rate of 10 ° C./second or less to obtain a negative electrode current collector having an average crystal particle diameter of the brass of 0.015 mm or more;
including.

In step (1), a wire rod made of brass, for example, is pressed into a nail mold having a predetermined size by a conventional method to obtain a nail mold body.
Steps (2) and (3) are preferably performed in a non-oxidizing atmosphere (for example, an inert gas atmosphere such as argon).
Step (2) is performed to recrystallize brass.
In order to prevent deformation of the molded body, the heating temperature in step (2) is preferably 400 ° C. or lower.

By adjusting the cooling rate after heating in the step (3), the average crystal particle diameter of brass can be easily controlled. In the step (3), the temperature drop in 1 second is controlled within 10 ° C. and gradually cooled.
In the step (3), it is preferable to cool the molded body to room temperature. From the viewpoint of productivity, the cooling rate in the step (3) is preferably 0.5 ° C./second or more. The cooling rate in step (3) is more preferably 0.5 to 3.3 ° C./second, particularly preferably 0.5 to 1.7 ° C./second.

In order to suppress the elution of brass into the electrolyte, a protective layer containing at least one selected from the group consisting of tin, indium, and bismuth is further formed on the surface of the negative electrode current collector after step (3). It is preferable to include the process (4) to form. The protective layer is preferably formed by a plating method.
The thickness of the protective layer is preferably 0.03 to 2 μm. When the thickness of the protective layer is less than 0.03 μm, it is easy to leak due to generation of hydrogen gas from the current collector when the battery is not used. When the protective layer contains tin, if the thickness of the protective layer is more than 2 μm, tin is eluted during overdischarge, the hydrogen generation overvoltage of zinc is lowered, and hydrogen gas is easily generated. When the protective layer contains at least one of indium and bismuth, if the thickness of the protective layer exceeds 2 μm, cost reduction becomes difficult.

The gasket 5 includes a central cylindrical portion 5a, an outer peripheral cylindrical portion 5b, and a connecting portion that connects the central cylindrical portion 5a and the outer peripheral cylindrical portion 5b. The body portion 6a of the negative electrode current collector 6 is press-fitted into the through hole of the central cylinder portion 5a.
The communication part has a thin part 5c that functions as a predetermined safety valve. When the battery internal pressure rises abnormally, the thin portion 5c provided in the connecting portion of the gasket 5 is broken, and gas can be discharged to the outside from the hole 7a of the negative electrode terminal plate 7.
The gasket 5 is obtained, for example, by injection molding nylon or polypropylene into a predetermined size and shape.

  The opening end portion of the battery case 1 is caulked to the peripheral edge portion (the flange portion) of the negative electrode terminal plate 7 via the outer peripheral cylindrical portion 5 b of the gasket 5. Thereby, the opening part of the battery case 1 is sealed. The outer surface of the battery case 1 is covered with an exterior label 8.

  The positive electrode mixture 2, the separator 4, and the gelled negative electrode 3 contain an alkaline electrolyte. The alkaline electrolyte is, for example, an aqueous potassium hydroxide solution. The concentration of potassium hydroxide in the electrolytic solution is preferably 30 to 40% by weight. The electrolytic solution may further contain zinc oxide. The concentration of zinc oxide in the electrolytic solution is preferably 1 to 3% by weight.

  The positive electrode mixture 2 contains at least one of manganese dioxide and nickel oxyhydroxide as a positive electrode active material. The positive electrode mixture 2 is made of, for example, a mixture of a positive electrode active material, a conductive agent, and an alkaline electrolyte. Graphite powder is used as the conductive agent.

  The gelled negative electrode 3 contains zinc or a zinc alloy as a negative electrode active material. The gelled negative electrode 3 is made of, for example, a gelled electrolyte obtained by adding a gelling agent to an alkaline electrolyte and a powdered negative electrode active material dispersed in the gelled electrolyte. As the gelling agent, for example, sodium polyacrylate is used.

In order to improve the corrosion resistance of the gelled negative electrode 3, the zinc alloy preferably contains 150 to 500 ppm of Al. Since Al exists on the surface of the active material particles, it becomes passive during overdischarge and delays dissolution of zinc. If the Al content of the zinc alloy is less than 150 ppm, the effect of improving the corrosion resistance of the gelled negative electrode 3 cannot be obtained sufficiently. When the Al content of the zinc alloy exceeds 500 ppm, Al may precipitate on the separator during discharge, resulting in a minute short circuit.
Furthermore, in order to improve the corrosion resistance of the gelled negative electrode, it is more preferable that the zinc alloy contains 50 to 500 ppm indium, 30 to 200 ppm bismuth, and 150 to 500 ppm aluminum.

The ratio of the capacity Cn of the gelled negative electrode to the capacity Cp of the positive electrode mixture (hereinafter Cn / Cp) is preferably 0.95 to 1.10. The capacity here indicates a theoretical capacity calculated based on the amount of active material.
As Cn / Cp is smaller, the utilization factor of the negative electrode active material during discharge is improved, the amount of unreacted zinc at the end of discharge is decreased, and the amount of gas generated from the gelled negative electrode is decreased. In order to significantly suppress gas generation from the gelled negative electrode, Cn / Cp is 1.10 or less, and the smaller the better. However, when Cn / Cp is less than 0.95, the utilization rate of the positive electrode active material becomes too low, and the discharge performance may deteriorate.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.
<< Examples 1-9 and Comparative Examples 1-2 >>
The AA alkaline battery (LR6) shown in FIG. 1 was produced by the following procedure.

(1) Preparation of negative electrode current collector A brass wire strip (manufactured by Sanetsu Metal Co., Ltd.) containing 65% by weight of copper and 35% by weight of zinc was pressed to form a nail mold (total length: 38.0 mm, trunk) Diameter: 1.15 mm).
The obtained molded body was heated at 300 ° C. for 10 minutes in a non-oxidizing atmosphere. Thereafter, the compact was gradually cooled to 25 ° C. At this time, the cooling rate of the compact was changed to the values shown in Table 1. In this way, negative electrode current collectors having different average crystal particle diameters were obtained.
Thereafter, a tin layer (thickness: 1.5 μm) was formed on the surface of the negative electrode current collector by plating.

[Measurement of average crystal particle size of negative electrode current collector]
(A) Pretreatment The epoxy resin surrounding the negative electrode current collector was cured, and the negative electrode current collector was embedded in the cured epoxy resin. Together with the cured product, the body of the negative electrode current collector was cut in a direction perpendicular to the axial direction. The cut surface was polished with a polishing paper and a buff to obtain a mirror surface state.
The cut surface of the negative electrode current collector exposed from the cured product was immersed in an etching solution for about 10 seconds, the cut surface was chemically treated, and then sufficiently washed with water. As the etching solution, a mixture of ammonia water (29 wt%), water, and hydrogen peroxide water (33 wt%) in a weight ratio of 1: 1: 0.02 was used. Then, it dried and removed the water | moisture content.

(B) Measurement of average crystal particle diameter An image of the cut surface was obtained with a polarizing microscope (Nicon Co., Ltd., Metaphont).
A line segment having a length of 100 μm was drawn at an arbitrary position in a predetermined region of the cut surface. The predetermined region was a region between the surface of the negative electrode current collector and a depth of 0.2 mm, that is, a ring-shaped region having a width of 0.2 mm from the outermost periphery to the inner periphery on the cut surface. The number of crystal particles completely separated by this line segment was counted. The value of (100 μm / number of crystal grains) was determined as the particle diameter. The above operation was repeated 5 times, and the average value was defined as the average crystal particle size.

(2) Preparation of positive electrode pellet Manganese dioxide powder (average particle size: 35 μm) and graphite powder (average particle size: 10 μm) were mixed at a weight ratio of 92.8: 6.2. And this mixture and alkaline electrolyte were mixed by the weight ratio of 99: 1, and after fully stirring, it compression-molded and obtained the flaky granulation mixture. A potassium hydroxide aqueous solution (KOH concentration: 35 wt%, ZnO concentration: 2 wt%) was used as the alkaline electrolyte for producing the positive electrode pellet.
Next, the flaky granulation mixture was pulverized into granules, which were classified by a sieve, and those having a size of 10 to 100 mesh were pressure-formed into a hollow cylinder to obtain positive electrode pellets.

(3) Preparation of gelled negative electrode Zinc alloy powder (average particle size: 170 μm) as a negative electrode active material, an alkaline aqueous solution as an alkaline electrolyte, and sodium polyacrylate powder as a gelling agent, 63.9: 35. The mixture was mixed at a weight ratio of 4: 0.7 to obtain a gelled negative electrode 3. As the zinc alloy, a zinc alloy containing 50 ppm Al, 150 ppm Bi, and 200 ppm In was used. A potassium hydroxide aqueous solution (KOH concentration: 35 wt%, ZnO concentration: 2 wt%) was used as the alkaline electrolyte for preparing the gelled negative electrode.

(4) Production of sealing unit 6,12-nylon was injection molded into a predetermined size and shape to obtain a gasket 5. A nickel-plated steel plate (thickness 0.4 mm) was pressed into a predetermined size and shape to obtain a negative electrode terminal plate 7. After the top portion 6b of the negative electrode current collector 6 is electrically welded to the flat portion at the center of the negative electrode terminal plate 7, the body portion 6a of the negative electrode current collector 6 is press-fitted into the through hole at the center of the gasket 5, and the sealing unit 9 is Produced.

(4) Alkaline battery assembly Two positive electrode pellets are inserted into the battery case 1, the positive electrode pellets are pressurized with a pressure jig and brought into close contact with the inner wall of the battery case 1, and positive electrode mixture 2 (10.4 g) Got. A bottomed cylindrical separator 4 (thickness: 250 μm) was placed inside the positive electrode mixture 2. An alkaline electrolyte (1.45 g) was injected into the separator 4. A potassium hydroxide aqueous solution (KOH concentration: 35 wt%, ZnO: 2 wt%) was used as the alkaline electrolyte for pouring.

After a predetermined time had elapsed, the gelled negative electrode 3 (6.00 g) was filled into the hollow portion of the positive electrode mixture 2 through the separator 4. For the separator 4, a non-woven fabric mainly composed of polyvinyl alcohol fiber and rayon fiber was used. After the opening end of the battery case 1 was sealed using the sealing unit 9, the outer surface of the battery case 1 was covered with the exterior label 8.
The capacity Cp of the positive electrode mixture 2 was 2.741 Ah. The capacity Cn of the gelled negative electrode 3 was 3.134 Ah. That is, Cn / Cp was 1.14.

[Evaluation]
(1) Assembly test of sealing unit 45,000 pieces of each negative electrode current collector were prepared. A sealing unit was assembled using these negative electrode current collectors. At this time, when the negative electrode current collector is pressed into the through hole of the gasket when the sealing unit is assembled, the tip of the negative electrode current collector is not inserted into the through hole, and the number of turns of the negative electrode current collector body is calculated. Counting was performed to determine the defect occurrence rate when the sealing unit was configured. This is because when the tip of the negative electrode current collector hits the periphery of the through-hole of the gasket and bending occurs, the negative electrode current collector body is pressed against the gasket in this state without correcting the minute bending. Occur.

(2) Measurement of gas generation amount during overdischarge Two batteries prepared as described above were prepared. A 10Ω resistor was connected to the assembled battery in which two batteries were connected in series, and the assembled battery was discharged in a 20 ° C. environment. The closed circuit voltage of each battery during discharge was monitored. After 3 days, the resistor was removed. The reversed battery was taken out and stored in a constant temperature bath at 45 ° C. for 1 week. The amount of gas generated during storage was measured by the water displacement method.
The evaluation results are shown in Table 1.

In the batteries of Examples 1 to 9 in which the average crystal particle diameter of the negative electrode current collector was 0.015 mm or more, gas generation during overdischarge was suppressed. In the batteries of Comparative Examples 1 and 2 in which the average crystal particle diameter of the negative electrode current collector was less than 0.015 mm, a large amount of gas was generated during overdischarge.
In the batteries of Examples 4 to 9 in which the average crystal particle size of the negative electrode current collector was 0.030 mm or more, the amount of gas generated during overdischarge was further reduced. In particular, in the batteries of Examples 7 to 9 in which the average crystal particle diameter of the negative electrode current collector was 0.045 mm or more, the amount of gas generated during overdischarge was greatly reduced.

Compared with the negative electrode collector used for the batteries of Comparative Examples 1 and 2, the negative electrode current collector used for the batteries of Examples 1 to 9 had a lower incidence of defects when the sealing unit was configured. This is because the negative electrode current collector used in the batteries of Examples 1 to 9 has a larger average crystal particle size and flexibility than the negative electrode current collectors used in the batteries of Comparative Examples 1 and 2. This is probably because when the negative electrode current collector is press-fitted into the through hole of the gasket, even if the tip of the negative electrode current collector is bent slightly, it is easily corrected.
In the negative electrode current collector having an average crystal particle diameter of 0.030 mm or more used for the batteries of Examples 4 to 9, the defect occurrence rate was further reduced. In particular, no defects occurred in the negative electrode current collector having an average crystal particle diameter of 0.045 mm or more used in the batteries of Examples 7 to 9.

<< Examples 10 to 15 >>
A battery was produced in the same manner as in Example 1 except that the diameter of the body part of the negative electrode current collector was changed. The amount of gas generated during overdischarge was determined by the same method as above.
The evaluation results are shown in Table 2.

  The smaller the body diameter, the smaller the contact area with the gelled negative electrode (electrolyte), so the amount of gas generated during overdischarge decreased. In particular, in the batteries of Examples 2 and 10-13 in which the diameter of the body of the negative electrode current collector was 0.95 to 1.35 mm, the amount of gas generated during overdischarge was greatly reduced.

<< Examples 16 to 20 >>
A battery was produced in the same manner as in Example 1 except that a zinc alloy having the composition shown in Table 3 was used as the negative electrode active material. The amount of gas generated during overdischarge was determined by the same method as above.

Moreover, the discharge test A of the following conditions was implemented.
In a 20 ° C. environment, the battery was discharged for 5 minutes with a load of 3.9Ω. This discharge was performed once per day. The above discharge was repeated until the closed circuit voltage of the battery reached 0.9V. And the total of discharge time until the closed circuit voltage of a battery reached 0.9V was calculated | required. The discharge time was expressed as an index with the discharge time of Example 2 as 100. If the discharge performance index was 80 or more, it was judged that the discharge performance was good.
The evaluation results are shown in Table 3.

  In all the batteries, the amount of gas generated during overdischarge decreased. In particular, in the batteries of Examples 17 to 19 in which the Al content in the zinc alloy was 150 to 500 ppm, the amount of gas generated during overdischarge was significantly reduced and good discharge performance was exhibited.

<< Examples 21 to 25 >>
The ratio of negative electrode capacity / positive electrode capacity (Cn / Cp) was changed. Specifically, as shown in Table 4, the amount of manganese dioxide in the positive electrode mixture was made constant, and the amount of zinc alloy in the gelled negative electrode was changed. A battery was manufactured in the same manner as in Example 1 except for the above. The amount of gas generated during overdischarge was determined by the same method as above.

Moreover, the discharge test B of the following conditions was implemented.
Under an environment of 20 ° C., the battery was continuously discharged with a load of 10Ω until the closed circuit voltage of the battery reached 0.9V. The discharge time at that time was determined. The discharge time was expressed as an index with the discharge time of Example 2 as 100. If the discharge performance index was 80 or more, it was judged that the discharge performance was good.
The evaluation results are shown in Table 4.

  In all the batteries, the amount of gas generated during overdischarge decreased. In particular, in the batteries of Examples 21 to 24 in which Cn / Cp was 0.95 to 1.10, the amount of gas generated during overdischarge was significantly reduced, and good discharge performance was exhibited.

  The alkaline dry battery of the present invention is suitably used as a power source for electronic devices such as portable devices.

DESCRIPTION OF SYMBOLS 1 Battery case 2 Positive electrode mixture 3 Gel-like negative electrode 4 Separator 5 Gasket 6 Negative electrode collector 7 Negative electrode terminal board 8 Exterior label 9 Sealing unit

Claims (10)

A hollow cylindrical positive electrode mixture containing a positive electrode active material;
A gelled negative electrode filled in the hollow part of the positive electrode mixture and containing a negative electrode active material;
A separator disposed between the positive electrode mixture and the gelled negative electrode;
A negative electrode current collector inserted into the gelled negative electrode;
A negative electrode terminal plate electrically connected to the negative electrode current collector;
An electrolyte,
An alkaline battery comprising:
The negative electrode current collector is made of brass having an average crystal particle diameter of 0.015 mm or more ,
The alkaline dry battery, wherein the brass contains 30 to 40% by weight of zinc .   The alkaline dry battery according to claim 1, wherein the brass has an average crystal particle diameter of 0.030 mm or more and 0.1 mm or less.   The alkaline dry battery according to claim 1, wherein an average crystal particle diameter of the brass is 0.045 mm or more and 0.1 mm or less. The negative electrode current collector is a nail type, and has a substantially cylindrical body part inserted into the gelled negative electrode, and a top part provided at one end of the body part,
The top is welded to the negative terminal plate;
The alkaline dry battery according to any one of claims 1 to 3, wherein a diameter of the body portion is 0.95 to 1.35 mm. The brass comprises 30 to 40% by weight of zinc, 0.05 to 3% by weight of at least one selected from the group consisting of tin, phosphorus and aluminum as optional components, and the balance copper and inevitable impurities. The alkaline dry battery in any one of -4.   The alkaline dry battery according to any one of claims 1 to 5, wherein the positive electrode active material contains at least one of manganese dioxide and nickel oxyhydroxide.   The alkaline dry battery according to claim 1, wherein the negative electrode active material contains zinc or a zinc alloy.   The alkaline dry battery according to claim 7, wherein the zinc alloy contains 150 to 500 ppm of Al.   The ratio of the capacity Cn of the gelled negative electrode to the capacity Cp of the positive electrode mixture: Cn / Cp is 0.95 to 1.10. The alkaline dry battery according to any one of claims 1 to 8. (1) obtaining a nail-shaped product made of brass containing zinc 30 to 40% by weight,
(2) heating the molded body to 300 ° C. or higher;
(3) After the step (2), the molded body is cooled at a rate of 10 ° C./second or less to obtain a negative electrode current collector having an average crystal particle diameter of the brass of 0.015 mm or more;
A method for producing an alkaline battery comprising:

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